I have just bought a JTV69 guitar second hand and it does not seem to have the USB interface with it. Where can I get one of these? What I would like to do is to tweak the models using the software. I have the software downloaded but I cannot connect the guitar to it. I tried a straight connection of ethernet cable to the computer but that did not work! Also, if I get an HD500x would that mean that I don't need a USB connection to get into the editing software?